Abstract 1840: In Vitro Cellular Implantation Assay To Quantitatively Compare The Ability Of Different Donor Cells To Electrically Conduct Within Cardiac Tissue
Cellular implantation is an emerging therapy for repair of the injured myocardium; however, the mechanisms of improvement and the optimal donor cell type remain unknown. We designed a reproducible, well-controlled in vitro assay for comparing the efficacy of different donor cell types to electrically couple with cardiomyocytes and propagate action potentials. Using soft lithography, we micropatterned 100um-wide strands of neonatal rat ventricular myocytes with an empty insert region of controlled length for donor cell attachment (implantation). Insert lengths were confirmed by immunostaining. Electrical conduction of Ca2+ transients or membrane voltage was optically mapped at 504 sites spaced 37um. The conduction time (CT) between two 638um spaced recording sites was measured in pure cardiac strands (control) and across inserts populated with different donor cell types. Control cardiac strands produced a CT of 2ms (conduction velocity of 30cm/s). Skeletal myoblasts and wild type HEK-293 cells, which express little or no connexin-43 (Cx43), produced conduction block at the insert. HEK-293 cells genetically engineered to overexpress Cx43 propagated action potentials with a CT of 25ms. Bone marrow mesenchymal stem cells had a CT of 18ms, and embryonic stem cell derived cardiomyocytes had the lowest CT of 40ms, likely due to their low level of Cx43 expression and/or immature ion channel properties. This novel assay allows for quantitative comparison of the intrinsic ability of different donor cells to conduct electrical activity and for mechanistic studies of the use of soluble factors and gene manipulations to control functional integration of donor cells within the heart.
This research has received full or partial funding support from the American Heart Association, AHA Mid-Atlantic Affiliate (Maryland, North Carolina, South Carolina, Virginia & Washington, DC).